1. Field of the Invention
The present invention relates to an apparatus and a method for delivering a web such as a wrapping paper or packing sheet used in the manufacture of cigarettes or packs.
2. Description of the Related Art
In the manufacture of cigarettes, a paper web delivered from a web roll is supplied to a cigarette manufacturing machine, and runs in one direction in a wrapping section of the machine. At the starting end of the wrapping section, Cut tobacco is fed onto the web. As the paper web runs, the cut tobacco is wrapped in the web, thus forming a continuous cigarette rod. Thereafter, the cigarette rod is cut into individual cigarettes with a predetermined length.
The paper web is delivered as a pulling roller is rotated with the web roll supported for rotation. As the roller rotates in this manner, the web is fed and delivered from the web roll which is rotating.
A braking force is applied to the web roll by means of a mechanical brake, such as a brake band or brake pad, and the web roll is rotated against the braking force. Accordingly, the paper web delivered from the web roll has a predetermined tension.
In order to maintain the quality of the cigarette rod formed in the wrapping section of the cigarette manufacturing machine and improve the yield of production thereof, the tension of the paper web delivered from the web roll should be stabilized. Unless the web tension is stable, the web supplied to the machine may possibly be slackened or caused to run in a zigzag line. Such slackening or meandering of the paper web prevents stable formation of the cigarette rod in the wrapping section, and in the worst case, causes breakage of the web, thereby interrupting the operation of the cigarette manufacturing machine.
In consideration of these circumstances, the paper web delivered from the web roll is expected to have a constant tension. The aforesaid mechanical brake can, however, apply only a fixed braking force to the web roll. As the diameter or mass of the paper web being delivered is reduced, therefore, the web tension also changes.
A further examination of the paper web tension revealed that the tensions varies according to a plurality of operation modes of a delivery apparatus which correspond to the operating conditions of the cigarette manufacturing machine.
In order to adjust the production of the cigarette rod, the cigarette manufacturing machine is operated at high and low speeds. Correspondingly, the delivery apparatus is operated in high- and low-speed modes. The pulling roller is rotated at one peripheral speed in one of these operation modes and at another in the other mode. The difference in the peripheral speed causes variation of the tension of the paper web delivered from the web roll.
The operation modes also include a stopping mode, during which the operation of the delivery apparatus is fully stopped following the high- or low-speed mode, and a suspension mode, in which the delivery of the paper web is in suspension. In the stopping mode, the paper web delivery is stopped as the peripheral speed of the pulling roller is gradually reduced. In doing this, the paper web is slackened unless the web roll is subjected to a braking force corresponding to its rotational mass. Also in the suspension mode, a braking force corresponding to the weight of the web roll should preferably be applied to the roll.
In order to stabilize the tension of the paper web, therefore, the braking force for the web roll should be controlled in consideration of the operation mode of the cigarette manufacturing machine as well as the variation of the mass of the roll.